Wildfires Fuel Climate Change

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The wildfires blazing through North Myrtle Beach, S.C., today are hardly an anomaly in a warming world. According to a landmark report that will be published tomorrow in Science, fires are not just a result of a changing climate, they're also contributing to the overall warming trend much more than imagined, the authors report. As vegetation burns, it releases stored-up carbon into the atmosphere, speeding global warming and thereby exacerbating conditions that may generate a greater incidence of wildfires in the coming years.

Because fires have been part of the global environment for hundreds of millions of years—since the first land plants emerged—as well as a tool for humans for more than 50,000 years, they're largely assumed to be a natural and negligible part of the carbon and climactic cycles. As people use fire on a massive scale as a cheap and efficient way to clear forests for agriculture or development, however, it is having a much greater impact than many scientists realized. In fact, deforestation fires alone have contributed 20 percent of the total greenhouse gases humans have contributed to the atmosphere since industrialization.

The report brought together 22 scientists from a range of disciplines and countries in an effort to better understand the global impact of fire. "This is a critical move away from the thinking that fires are just a disaster," says David Bowman, a professor of forest ecology at the University of Tasmania in Hobart, Australia, and a lead author of the report. Taken in isolation, each conflagration can cause massive human, economic and natural devastation, but as a broader force fire wields a much larger power, according to the report. "Fire is a feature of our planet…. High levels of fire activity have the capacity to change climate," he says.

But across the globe, fires have been getting larger and stronger. "We are witnessing an increasing instance of these megafires," says Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona. This year alone has seen an increase in both the magnitude and deadliness of conflagrations sweeping Australia and the U.S. Southwest. In the past 20 years, the area scorched by fire in the western U.S. was six times greater than in the two decades that preceded it. These infernos are in large part a result of longer, drier summers, which are only poised to get worse with climate change, Swetnam explains.

"The real originality of this work is that we've been able to say something so obvious," Bowman says. He noted that the challenge now will be integrating fire into the large-scale climate models, and that will take further research and understanding.

"What we're calling for," said Bowman of the report, "is inclusion [of fire] in the next [Intergovernmental Panel on Climate Change] models." Not only is the fire of a broader concern for climate stability and human well-being, but large-scale events also pose a risk of upsetting new carbon trading schemes, notes Jennifer Balch, a postdoctoral fellow at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, because they can release huge amounts of carbon dioxide into the atmosphere with one fell poof.